Single switch controlled switched reluctance machine

Abstract

An improved single-switch control circuit for use in a multi-phase switched reluctance machine is provided. The control circuit includes at least first and second phase windings, a switch, a capacitor, and a diode. The capacitor may have a polarity opposite that of a power source in the control circuit. The first winding may be connected in series with the switch and connected in parallel with a circuit block comprising the second winding. The second winding may be connected in parallel with the capacitor and in series with the diode. In operation, the switch may be used to redirect current from the first winding to the second winding. The capacitor can become charged by the redirected current until it eventually stores enough energy to essentially discontinue current flow in the first winding. Then, the capacitor can discharge its stored energy as a current through the second winding. In this manner, substantially all of the energy from the first winding can be transferred to the second winding.

What is claimed is: 
     
       1. An electrical device comprising:
 a switch; 
 a unidirectional current element that conducts current unidirectionally; and 
 a capacitive storage element, wherein: 
 the switch, unidirectional current element, and capacitive storage element are interconnected, with no direct electrical connection between the switch and capacitive storage element, such that when interconnected with a direct current (dc) voltage supply and first and second windings:
 a first operational state exists in which a conductive condition of the switch causes the dc voltage supply to conduct current through the first winding and switch, thereby storing energy in the first winding, 
 a second operational state exists in which a non-conductive condition of the switch causes the first winding to discharge stored energy by conducting current through the unidirectional current element and capacitive storage element, thereby storing energy in the capacitive storage element, and 
 a third operational state exists in which energy stored in the capacitive storage element is discharged by the conduction of current through the second winding, without conducting current through the dc voltage supply, and 
 
 at all times during the first, second, and third operational states, the second winding is electrically connected in parallel with the capacitive storage element such that a voltage existing across the second winding is the same voltage existing across the capacitive storage element. 
 
     
     
       2. The electrical device of  claim 1 , further comprising:
 a dc storage capacitance, wherein 
 the dc storage capacitance and capacitive storage element have direct electrical connectivity but do not conduct current through an electrical circuit that is common to both the dc storage capacitance and capacitive storage element. 
 
     
     
       3. The electrical device of  claim 1 , wherein the current conducted through the unidirectional current element and capacitive storage element during the second operational state is not conducted through the dc voltage supply. 
     
     
       4. The electrical device of  claim 1 , wherein the energy stored in the capacitive storage element is discharged by the conduction of current through an electrical circuit consisting essentially of the capacitive storage element and second winding. 
     
     
       5. An electrical device comprising:
 first and second windings; 
 a unidirectional current element that conducts current unidirectionally; 
 a switch that is directly connected with the first winding and the unidirectional current element; and 
 a capacitive storage element, wherein: 
 at all times when a direct current (dc) voltage supply is provided to the electrical device:
 the second winding is electrically connected in parallel with the capacitive storage element such that a voltage existing across the second winding is the same voltage existing across the capacitive storage element, and 
 the capacitive storage element and unidirectional current element are electrically connected in parallel with the first winding such that a voltage existing across a series connection of the capacitive storage element and unidirectional current element is the same voltage existing across the first winding. 
 
 
     
     
       6. The electrical device of  claim 5 , wherein when the dc voltage supply is provided to the electrical device:
 a first operational state exists in which a conductive condition of the switch causes the dc voltage supply to conduct current through the first winding and switch, thereby storing energy in the first winding, 
 a second operational state exists in which a non-conductive condition of the switch causes the first winding to discharge stored energy by conducting current through the unidirectional current element and capacitive storage element, thereby storing energy in the capacitive storage element, and 
 a third operational state exists in which energy stored in the capacitive storage element is discharged by the conduction of current through the second winding, without conducting current through the dc voltage supply. 
 
     
     
       7. The electrical device of  claim 6 , wherein the current conducted through the unidirectional current element and capacitive storage element during the second operational state is not conducted through the dc voltage supply. 
     
     
       8. The electrical device of  claim 6 , wherein the unidirectional current device prevents the capacitive storage element from conducting current through the first winding. 
     
     
       9. The electrical device of  claim 6 , wherein the energy stored in the capacitive storage element is discharged by the conduction of current through an electrical circuit consisting essentially of the capacitive storage element and second winding. 
     
     
       10. The electrical device of  claim 5 , wherein the first and second windings are constituents of a single phase of an electrical machine. 
     
     
       11. The electrical device of  claim 5 , wherein when the dc voltage supply is provided to the electrical device:
 a first operational state exists in which a conductive condition of the switch causes the dc voltage supply to conduct current through the first winding and switch, thereby storing energy in the first winding, 
 a second operational state exists in which a non-conductive condition of the switch causes the first winding to discharge stored energy by conducting current through the unidirectional current element and capacitive storage element, without conducting current through the dc voltage supply, thereby storing energy in the capacitive storage element, and 
 a third operational state exists in which energy stored in the capacitive storage element is discharged by the conduction of current through the second winding. 
 
     
     
       12. The electrical device of  claim 11 , wherein the energy stored in the capacitive storage element is discharged by the conduction of current through an electrical circuit consisting essentially of the capacitive storage element and second winding. 
     
     
       13. The electrical device of  claim 5 , further comprising:
 third and fourth windings; 
 another unidirectional current element that conducts current unidirectionally; and 
 another capacitive storage element, wherein: 
 when the dc voltage supply is provided to the electrical device:
 the fourth winding is electrically connected in parallel with the other capacitive storage element, and 
 the other capacitive storage element and the other unidirectional current element are electrically connected in parallel with the third winding, and 
 
 each of the first through fourth windings is a distinct winding of a four-phase electrical machine. 
 
     
     
       14. The electrical device of  claim 5 , further comprising:
 third and fourth windings; 
 another unidirectional current element that conducts current unidirectionally; and 
 another capacitive storage element, wherein: 
 when the dc voltage supply is provided to the electrical device:
 the fourth winding is electrically connected in parallel with the other capacitive storage element, and 
 the other capacitive storage element and the other unidirectional current element are electrically connected in parallel with the third winding, 
 
 the first and second windings are constituents of a single, first-phase of an electrical machine, and 
 the third and fourth windings are constituents of a single, second-phase of the electrical machine. 
 
     
     
       15. A method of operating an electrical motor, the method comprising:
 executing a first operation in which a conductive state of a switch causes a direct current (dc) voltage supply to conduct current through a first winding of the electrical motor and the switch, thereby storing energy in the first motor winding; 
 executing a second operation in which a non-conductive state of the switch causes the first motor winding to discharge stored energy by conducting current through a capacitive storage element, thereby storing energy in the capacitive storage element; and 
 executing a third operation in which energy stored in the capacitive storage element is discharged by the conduction of current through a second winding of the electrical motor, without conducting current through the dc voltage supply, wherein 
 at all times during the first, second, and third operations, the second winding is electrically connected in parallel with the capacitive storage element such that a voltage existing across the second winding is the same voltage existing across the capacitive storage element. 
 
     
     
       16. The method of  claim 15 , wherein the current conducted through the capacitive storage element during the second operation is not conducted through an energy storage element of the dc voltage supply. 
     
     
       17. The method of  claim 15 , wherein the discharge of energy stored in the capacitive storage element does not conduct current through the first motor winding. 
     
     
       18. The method of  claim 15 , wherein the energy stored in the capacitive storage element is discharged by the conduction of current through an electrical circuit consisting essentially of the capacitive storage element and the second winding. 
     
     
       19. A method of operating an electrical motor, the method comprising:
 executing a first operation in which a conductive state of a switch causes a direct current (dc) voltage supply to conduct current through a first winding of the electrical motor and the switch, thereby storing energy in the first motor winding; 
 executing a second operation in which a non-conductive state of the switch causes the first motor winding to discharge stored energy by conducting current through a capacitive storage element, without conducting current through the dc voltage supply, thereby storing energy in the capacitive storage element; and 
 executing a third operation in which energy stored in the capacitive storage element is discharged by the conduction of current through a second winding of the electrical motor, wherein 
 at all times during the first, second, and third operations, the second winding is electrically connected in parallel with the capacitive storage element such that a voltage existing across the second winding is the same voltage existing across the capacitive storage element. 
 
     
     
       20. The method of  claim 19 , wherein the discharge of energy stored in the capacitive storage element does not conduct current through the first motor winding. 
     
     
       21. The method of  claim 19 , wherein the energy stored in the capacitive storage element is discharged by the conduction of current through an electrical circuit consisting essentially of the capacitive storage element and the second winding.